Note: Descriptions are shown in the official language in which they were submitted.
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RETRO-REFLECTIVE SIGN
BACKGROUND OF INVENTION
This invention relates to a retro-reflective sign particularly useful as a
road
sign which is made visible at night by reflecting automotive vehicle light
beams.
Conventional highway signs, such as stop signs, one-way or wrong-way
signs, informational type of signs such as indicating distances or highway
exits and
the like, are made of panels upon which the sign information or indicia is
painted or
otherwise imprinted. Such signs may also have standard recognized shapes
which,
themselves, indicate the type of message, such as a stop sign with an
octagonal
peripheral shape.
In order to make such signs more visible to vehicle drivers at night, it is
conventional to make the signs reflective by utilizing special reflective
paints or
reflective coatings or beads. Thus, beams of light from the headlights of a
vehicle
are reflected from the sign panels, so that the messages or indicia are more
readily
visible to the vehicle driver as the vehicle approaches the sign. In order to
make
such sign messages visible at maximum distances, it is desirable to make the
signs as
reflective as possible. Thus, various techniques have been used to increase
the
reflectivity of the signs, so that their messages are brightly illuminated.
One known light reflective system involves the use of retro-reflective cube
corner configurations impressed within the rear surface of a relatively
transparent sign
panel or lens panel. Incoming or incident light rays from an automotive
vehicle light
beam, which strike the exposed face of the panel, pass through the panel to
the cube-
corner retro-reflective configurations, located on the rear face of the panel,
and are
reflected back through the panel towards the source of the light. The light
rays
entering the cube corners are bounced from one surface to another and are
reflected
back approximately parallel to the corresponding incoming rays.
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Examples of retro-reflective road signs are disclosed in U.S. Patent No.
5,442,870 issued August 22, 1995 to George E. Kochanowski for a "Reflective
Sign." Other examples of the use of cube-corner, retro-reflective types of
reflective
signs or panels are disclosed in U.S. Patent No. 2,167,149 to Walter F. Grote,
issued
July 25, 1939 for a "Total Reflecting Prism Sheet"; U.S. Patent No. 2,193,057
issued March 12, 1940 to Horace N. Carver for a "Sign"; U.S. Patent No.
3,772,810
issued November 20, 1973 to Sam Kupperman, et al. for a "Reflecting Figure to
be
Applied to a Support Surface"; and U.S. Patent No. 3,970,033 issued July 20,
1976,
to Henry Linder, et al. for a "Portable Reflector Device. " Another use of
such type
of reflective device is illustrated in U.S. Patent No. 3,409,344 issued
November 5,
1968 to Rudolf Douglas Balint for "Roadway Reflectors" used to mark the
surfaces
of pavements.
The prior retro-reflective signs, generally, reflect light by passage of the
incoming or incident rays of light from an automotive vehicle headlight beam,
through the front surface of a panel, then through the panel to the cube-
corner
reflective rear surface configurations. The light rays bounce between the
three walls
making up each cube corner and then are reflected back through the panel and
out the
front face in approximate parallelism to the incoming light rays. That is,
corresponding incoming and outgoing light rays are roughly parallel.
It is desirable to direct the incoming rays as parallel as possible to the
cube
axes so that they reflect parallel to their respective cube axes. This
provides for
maximum intensity of reflection. There is a tendency for the reflected light
rays to
scatter or reflect at an angle relative to the driver of the vehicle which is
the source
of the incoming rays, rather than to be directed back toward the source of the
light
and the driver's view. This reduces the intensity of the reflection and
correspondingly, the distance at which the reflected message on the sign may
be
clearly seen.
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Thus, this present invention is concerned with improving the construction of
the lens panel of a retro-reflective sign to better direct and intensify the
reflected
light. In general, this construction functions to initially bend and direct
incoming
light beams into approximate parallelism with the vertical axes of their
respective
cube-corner configurations and, then, to re-bend the reflected light coming
from the
cube corners towards the source of the light so as intensify the reflection
and increase
the distance at which the sign message is plainly visible.
In addition, this invention is concerned with improving the physical strength
of a highway sign which is formed of molded plastic material and to make the
sign
message more visible to oncoming drivers by utilizing ambient light to
backlight a
sign message that may be molded or otherwise formed on the sign panel. That
is,
large sign panels which are formed of thin plastic sheet-like material are
relatively
weak. Since road signs are subject to intermittent relatively high forces,
such as
strong winds (which tend to damage the sign panels), this invention provides
an
integrally molded surface configuration on the sign panel and a separate
support or
backing panel which substantially rigidifies and strengthens the sign panel.
Furthermore, the support panel may assist in utilizing ambient light to
intensify the
readability of the sign message.
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SUMMARY OF INVENTION
This invention relates to a retro-reflective sign having a front lens or sign
panel, which
may be molded out of a transparent plastic material, and a rear support or
backing panel which
may be translucent or opaque. The rear surface of the lens panel is formed
with a pattern of
adjacent cube-corner configurations which reflect light rays, and raised ribs
or beads which
form a honeycomb pattern surrounding groups of cube corner configurations. The
front surface
of the lens panel may be smooth or, alternatively, may be formed with integral
prism, such as
wedge-like or saw-tooth prism shapes. The prism shapes bend incoming light
rays toward the
cube axes which results in increasing the intensity of the reflected light.
This maximizes
visibility to the approaching vehicle driver; particularly in the case of
overhead or raised type
signs.
Further, this invention may provide a rigid, strong, sign construction by
forwardly
bowing the lens panel and attaching to the lens panel a rearwardly bowed
support or backing
panel. The two panels may be joined together along their peripheral edges. In
addition, one or
more ribs are integrally formed on the backing panel to increase the strength
and rigidity of the
combined panels.
The backing or support panel may be made of a translucent plastic material
which will
pass some ambient light to the rear, and through, the lens panel. For example,
sunlight passing
through the backing panel can backlight or further illuminate the sign message
formed on the
translucent lens panel.
This invention may provide a roadway sign, such as a stop sign or the like,
which is
formed of a pair of oppositely bowed, overlapped panels or plates that are
connected together
along their adjacent edges. One plate forms a front -- message bearing -- lens
panel having
molded cube-corner retro-reflective configurations formed on its rear face
and, optionally, saw-
tooth shaped prisms formed on its front face for intensifying and directing
reflecting light rays
striking the lens panel. The two joined plates provide a unitary wind-
resistant, strong and rigid
sign.
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The invention may provide a molded plastic highway sign having a forwardly
bowed
lens panel with a reflective rear face and a light ray bending or focusing
front face for
intensifying and directing reflected light rays towards an incoming light ray
source, such as an
automotive vehicle headlights, and a rearwardly bowed backing panel joined to
the lens panel.
Preferably, the backing panel is made of a molded plastic material which is
translucent or
transparent so that it transmits some light to backlight indicia on the lens.
The invention may provide a plastic molded sign having a transparent,
forwardly bowed
message bearing lens panel formed with a retro-reflective rear surface made of
a pattern of
grooves of impressed reflective corner cube configurations with raised ribs
surrounding and
separating the groups, and a rearwardly bowed backing panel overlapping the
lens panel, with
the two panels joined together along their peripheral edges to form a unitary
sign construction.
Optionally, the backing panel may be formed of a light passing plastic
material which may
permit ambient light to backlight the lens panel.
The invention may form a reflective highway sign having a front, transparent,
lens panel
bearing message indicia formed of patterns of reflective cube-corner
configurations impressed
on the rear face of the lens panel and a rear support panel that overlaps and
is spaced from, but
is joined to the lens panel. A honeycomb pattern of ribs may be molded on the
rear face of the
lens panel and radially directed ribs molded on the forward face of the
support panel rigidifies
and strengthens the panels and the sign construction.
The invention may provide a reflective sign which is more visible both at
night and in
the day than what conventional signs are, and which is extremely sturdy and
wind resistant, and
which has exposed surfaces that are easily cleaned, so as to improve the
useable life of a
highway sign.
Accordingly, in one aspect there is provided a retro-reflective sign
comprising a lens
plate with sign indicia molded within the lens plate, and having a front face
and a rear face, said
rear face being molded with a plurality of adjacent, retro-reflective cube
corner configurations,
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defined by three intersecting walls of a cube which have a central axis, which
configurations
reflect incoming light rays that enter the plate through its front face and
pass through the plate
to its rear face and whose configurations reflect the light rays back through
the plate and its
front face generally towards the incoming light rays, said rear face of the
lens plate further being
molded with a protrusion extending opposite from the front face, the
protrusion extending about
the periphery of the lens plate; a plurality of substantially continuous,
raised ribs formed
integral with the rear face of the lens plate and arranged in honeycomb
patterns which surround
groups of cube corner configurations so that numerous configurations are
located within and
outside of each honeycomb pattern; and a rear support plate connectable to the
lens plate, the
support plate having a plurality of radially extending stiffening ribs
extending continuously
from a middle of the support plate to outer peripheral edges of the support
plate so as to
reinforce the support plate, the outer peripheral edges of the support plate
having a groove that
is operable to receive said protrusion and for securing the lens plate and the
support plate
together.
In another aspect, there is provided a retro-reflective sign molded from a
single plastic
resin comprising a light reflecting lens plate having a front face and a rear
face being cube
cornered and a plurality of groups of adjacent, cube corner retro-reflective
configurations
molded on said rear face for providing light-reflective areas, with the front
face of the lens plate
being colored in certain areas to spell out words on the sign and with the
areas surrounding the
words being made of material that is not of the same color, the lens plate
further having an edge
rim with an outwardly extending protrusion about the periphery of the lens
plate; prisms
integrally molded on the front face of the lens plate and shaped to bend
incoming light rays
towards central axes of the respective cube corners which the respective
prisms overlap; and
a support plate spaced apart from the lens plate, the support plate having at
least one rib
integrally molded and extending continuously from a middle of the support
plate to an outer
edge of the support plate, the outer edge of the support plate having a groove
that mates with
the protrusion extending from the periphery of the lens plate.
In a further aspect, there is provided a retro-reflective sign comprising: a
lens plate with
sign indicia molded within the lens plate, the lens plate having a front face
and a rear face, the
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rear face being molded with a plurality of adjacent, retro-reflective cube
corner configurations,
defined by three intersecting walls of a cube which have a central axis, a
plurality of
substantially continuous, raised ribs formed integral with the rear face of
the lens plate and
arranged in honeycomb patterns which surround groups of cube corner
configurations, the lens
plate further having a tongue extending about its entire perimeter; and a back
plate connectable
to the lens plate, the back plate having a continuous edge rim located about
its outer periphery
with a u-shaped groove that is operable to receive the tongue of the lens
plate in order to secure
the lens and back plate together, a plurality of radially extending stiffening
ribs extending
continuously from a center of the back plate to the edge rim for reinforcing
the back plate.
These and other features and advantages of this invention will become apparent
upon
reading the following description, of which the attached drawings form a part.
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DESCRIPTION OF DRAWINGS
FIG. 1 is a front, elevational view of a stop sign.
FIG. 2 is a rear, elevational view of a stop sign.
FIG. 3 is a rear, elevational view of the front or lens plate of the sign
taken
in the direction of Arrows 3-3 of Fig. 5.
FIG. 4 is a front, elevational view of the backing or support plate.
FIG. 5 is an enlarged, cross-sectional, schematic view of the sign taken in
the direction of Arrows 2-2 of Fig. 1, with the bowing of the plates being
exaggerated for illustration purposes.
FIG. 6 is an enlarged, schematic, fragmentary view of an edge portion of the
sign showing prism formations formed on the front face of the lens plate.
FIG. 7 is an enlarged, schematic, fragmentary view of the lens and backing
plates separated, with the front face of the lens plate formed smooth rather
than with
prisms.
FIG. 8 is a cross-sectional, schematic elevational view showing the front lens
plate, separated from the rear backing plate.
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FIG. 9 is an enlarged, cross-sectional, schematic, fragmentary view of the
front and the rear plates, joined together.
FIG. 10 is an enlarged, schematic cross-sectional view of the fastening
section of the sign for fastening the sign upon a support post.
FIG. 11 is an enlarged, elevational view of a fragment of the rear surface of
the lens plate illustrating the honeycomb reinforcing rib pattern.
FIG. 12 is an enlarged, schematic view of a cross-sectional fragment of the
lens plate showing the front and rear surfaces of the plate, with prisms
formed on the
front surfaces.
FIG. 13 is a further enlarged view of a fragment of the lens plate, shown in
cross-section, and schematically illustrating the movement of light rays into
and out
of the lens plate.
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DETAILED DESCRIPTION
Referring to the drawings, Fig. 1 illustrates a front view of a stop sign 10
which is formed in a conventional octagonal shape. This sign has indicia 11,
which
spell the word "stop," and a border 12 adjacent the peripheral edge of the
sign. The
indicia and the border may be clear or white while the field or area 13
surrounding
the indicia and contained within the border, may be colored red as is
conventional on
stop signs. The sign may be made in a number of colors and the indicia may be
varied, depending upon the type or purpose of the sign. Similarly, the shape
of the
sign may be round or square or rectangular, depending upon the type of sign
and the
message to be given by the sign.
The sign is formed of a front, or forward, lens panel or plate 15 and a rear
backing or support plate or panel 16. The two plates are formed of molded
plastic,
such as of a conventional polycarbonate plastic material used for molded
signs. The
two plates overlap and are secured together along their peripheral edges.
A preferred form of securement of the plates comprises an edge rim or bead
17 formed on the lens plate (see Fig. 6). The rim has a tongue 18 which may be
continuous. The backing plate is provided with an edge rim 19 having a groove
20
which receives the tongue 18. The tongue and groove connection may be held
together by a suitable adhesive or by a frictional, interference type of fit
of the tongue
within the groove or by ultrasonic welding.
The plates 15 and 16 are preferably bowed in opposite directions. Thus,
preferably each plate is a segment of a sphere of a large radius. The bowing
of the
plates is exaggerated in the schematic illustrated in Fig. 5. The amount of
bowing
would be determined by the sign designer, and would take into consideration
the
thickness of each of the plates, the size of the signs, and the intended
strength of the
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sign. For example, a stop sign may be about 30 inches in diametrical direction
with
the bowing radii of the two plates being approximately 40 feet, and the plates
having
a wall thickness of about 0.16 inches. The curvature and the thickness of each
of the
plates may vary, depending upon size and strength requirements.
The bowing of the plates, even though a relatively small amount of curvature,
strengthens the sign and enables the sign to withstand substantial wind gusts
or wind
forces applied against the sign as well as reducing the glare from any light
source.
Preferably, the backing plate is provided with raised beads or ribs 21 which
may be radially arranged to extend from approximately the middle of the plate
towards the peripheral edges of the plate. These raised ribs stiffen and
reinforce the
backing plate.
In addition, spaced apart projections or spacers 22 may be molded or
otherwise joined to the forward face of the backing plate to engage the rear
of the
lens plate. The lengths of the projections vary to bridge the length of the
space
between the plates at the locations of the respective projections. To attach
the sign
to a support post 23 (schematically shown in Fig. 9 and 11) threaded socket
members
24 are formed on the forward surface of the backing plate to receive fastening
screws
or the like 25 in threaded openings 26. Fins 27 connect the socket members to
the
backing plate for reinforcement purposes. In addition, integral pads 28 molded
on
the rear face of the backing plate form seats for the support post. The size
and
thickness of the pads 28 will vary, depending upon the type of mounting posts
or
other support devices that may be used for the sign.
The lens plate 15 has a front, exposed face 30 and a rear face 31. The rear
face 31 is molded with a pattern of adjacent, depressed, cube corners which
form a
retro-reflective configurations 32 (see Fig. 6). Such configurations are
conventional.
Cube corner reflective surfaces function to reflect rays of light passing
through a lens
plate to the reflective rear surface of the plate, which is provided with the
depressed
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retro-reflective cube corners. The sizes and the locations or patterns of the
cube
corners may be varied, depending upon the size and shape of the sign and its
indicia.
The rear face 31 of the lens plate is also provided with raised ribs 33 which
form a honeycomb type pattern, imposed around the pattern of cube corners. The
ribs may be formed in pattern in the shapes of hexagons or other geometric
shapes
which surround, and are surrounded by, the cube corner configurations. In
addition,
an edge bead or rib 35 is formed adjacent the peripheral edge of the lens
plate, as is
schematically shown in Figs. 3 and 11. Similarly, edge beads or ribs 36 are
molded
integrally with the rear face of the lens plate around each of the letters
forming the
indicia or message (see Fig. 3).
In one modification, the front face 30 of the lens plate 15 is formed with a
plurality of wedge-shaped, saw-tooth in cross-section shape, prisms 40. These
prisms
may be in the form of rows or strips extending across the front face of the
lens plate.
These prisms cooperate with the cube corner configuration, as will be
described
below, in reflecting incoming light rays.
The reflection of light rays is schematically shown in Fig. 13. Each of the
cube comers has a central axis 41. An incoming light ray 42, which may come
from
an automobile headlight beam, strikes one of the prisms 40 on the exposed or
forward
surface of the lens. The prism bends the incoming light beam into a light ray
portion
43 which travels transversely through the plate, substantially parallel to the
cube
corner axis 41, to contact a cube corner wall 44. The ray portion 45 is
reflected to
the opposite cube corner wall 46 from which the ray portion 47 is reflected
back,
approximately parallel to the cube corner axis 41, through the lens panel to
the prism
40. The prism 40 re-bends the reflected light ray to form a reflected ray 48
directed
towards the source of the light, that is, towards the automotive vehicle light
beam and
approximately parallel to the incoming ray portion 42.
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The intensity of the visible reflection is substantially increased because the
incoming and returning light ray portions 42 and 48 are approximately parallel
to the
central axes 41 of the corner cubes which they strike (see Fig. 13).
In essence, the corner cube retro-reflective configuration receives a light
ray,
which passes through the lens, and then, the ray is bounced within the cube
structure
and reflected outwardly, roughly parallel to the incoming ray. However, where
the
ray enters a corner cube at an angle relative to the axis of the cube, it
similarly leaves
at approximately the same angle and, consequently, is dispersed or reflected
at an
angle relative to the headlight beam of the vehicle.
If the reflected light beam is directed towards the vehicle which is the
source
of the headlight beam, as seen by the driver, the visibility or intensity of
the reflected
light is substantially greater than where the light ray is reflected at an
angle to the
source. In this case, the term "intensity" is meant to refer to the visibility
or visual
brightness of the reflected light to the vehicle driver who is located at a
distance
rearwardly of the headlight beam light source. Hence, returning the light in
the
direction of the headlight beam, intensifies or brightens the reflection seen
by the
vehicle driver so that the driver may see the reflected light at a greater
distance than
otherwise and the driver may see it more sharply than otherwise.
In a second modification of the lens plate front face, as shown in Figs. 7 and
9, the surface 50 is smooth rather than formed with the prisms illustrated in
Fig. 6.
In this type of sign structure, the indicia or wordings on the sign, as
compared with the areas surrounding the indicia, may be molded of a different
color
plastic, using known plastic molding techniques. For example, the indicia may
be
clear or white, by using clear transparent plastic or white colored plastic
and the
surrounding field may be red by using red colored plastic to produce a stop
sign.
Alternatively, green or blue colored plastics may be used to produce an
informational
type of sign.
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Further, despite the sign being formed of thin panels made of a molded
plastic material, the sign is considerably strengthened by the pattern of ribs
or beads
formed in and around the reflective cube corner co~guration and the letters
forming
the indicia on the lens plate. The strength of the composite, two plate, sign
and its
resistance to wind loads and other forces is further increased by the bowing
of the
two plates or panels and the rib structure on the backing plate. The rows of
prisms
preferably are curved to follow the curvature of the lens plate for bending
incoming
light rays into approximate parallelism with the respective overlapped cube
corners
and for re-bending reflected rays from such cube corners.
The molded plastic sign construction may be easily cleaned or maintained and
its exposed surfaces will tend to shed dirt and moisture so as to be self
cleaning when
subjected to rain. Hence, the foregoing sign construction will provide a
strong, wind-
resistant, easily cleaned, construction.
This invention may be further developed within the scope of the following
claims. Accordingly, it is desired that the foregoing description be read as
merely
illustrative of an operative embodiment of this invention and not in a
strictly limiting
sense.
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